Duan, AY (reprint author), Univ Chinese Acad Sci, Key Lab Computat Geodynam, Beijing 100049, Peoples R China.
; Duan, AY (reprint author), Chinese Acad Sci, SIGMA Weather Grp, Natl Space Sci Ctr, State Key Lab Space Weather, Beijing 100190, Peoples R China.
; Duan, AY (reprint author), Univ Alabama, Ctr Space Plasma & Aeron Res, Huntsville, AL 35899 USA.
National Natural Science Foundation of China [41604140, 41531073, 41374176, 41574170, 41231068, 41574171]
; China Postdoctoral Science Foundation [119103S277]
; Specialized Research Fund for State Key Laboratories
英文摘要:
Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field, which is difficult to directly measure. Various analytic models and numerical codes exist, but their results often drastically differ. Thus, a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a nonlinear force-free field code (CESE-MHD-NLFFF) and a non-force-free field (NFFF) code, in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from the region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO/AIA. It is found that the CESE-MHD-NLFFF code with preprocessed magnetogram performs the best, outputting a field that matches the coronal loops in the AR core imaged in AIA. 94 A with a misalignment angle of similar to 10 degrees. This suggests that the CESE-MHD-NLFFF code, even without using the information of the coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA. 171 A in the outskirts of the AR, all the codes including the potential field give comparable results of the mean misalignment angle (similar to 30). Thus, further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.
